Document EP 1 679 153 discloses a trimming device of the aforementioned type, in which the rotation clamping and driving means for clamping and driving the rotation of the lens comprise two coaxial shafts designed to sandwich the ophthalmic lens.
The trimming device described in that document comprises a set of grinding wheels for roughing and chamfering the lens and two feeler rods respectively intended to come into contact with the front and rear optical faces of the lens in order to measure the geometry thereof.
The set of grinding wheels and the two feeler rods are for that reason each equipped with drive means and with measurement means which are specific to them.
In that document, the tool holder of the trimming device comprises a support flanked, on one side, by a grooving wheel (the “first tool”) and, on the other side, by a drill bit (the “second tool”). These two finishing tools can therefore be selected by causing the support to pivot through 180 degrees about the axis of pivoting using drive means specific to it.
One disadvantage of this device is that it comprises a great many drive means, to the detriment of its cost of manufacture and assembly and to the detriment of its bulk.
The major disadvantage of this device is that the tool holder is of such a bulk that the grooving wheel and the drill bit cannot be brought as close as would be desired to the ophthalmic lens clamping shafts. As a result, when the lens is of small height, it may prove to be impossible to groove the lens around its entire contour or to drill a hole in it, because the tool holder comes into contact with the clamping shafts.
The applicant company has also observed that, even when the bulkiness of these tool holders is reduced, it might not be possible to bring the drill bit as close as might be desired to the lens clamping shafts. Specifically, since the diameter of the grooving wheel is greater than that of the drill bit it may happen that the grooving wheel comes into contact with the clamping shafts before the drill bit reaches the desired position.